1. Field of the Invention
The present invention relates to a mechanism for locking the hub of a removable disk cartridge to the spindle motor of a disk drive upon spin-up of the motor to prevent separation of the hub and spindle motor during high speed rotation.
2. Description of the Prior Art
Removable disk cartridges for storing digital electronic information typically comprise an outer casing or shell that houses one or more rotatable storage mediums, or disks, upon which electronic information can be stored. The cartridge shell often comprises upper and lower halves that are joined together to house the disk(s). The disk(s) is mounted on a hub assembly that rotates freely within the cartridge. The outer shell of the cartridge typically has some form of opening near its forward edge to provide the recording heads of the drive with access to the recording surfaces of the disk. A shutter or door mechanism is often provided to cover the opening when the cartridge is not in use to prevent dust or other contaminants from entering the cartridge and settling on the recording surface of the disk.
When the cartridge is inserted into a data storage device, i.e., disk drive, a spindle motor in the drive engages the hub assembly through an opening in the bottom shell of the disk cartridge in order to rotate the disk within the cartridge. In many prior art removable cartridge disk drive systems, a center spindle on the motor engages a through-hole in the hub assembly, and a chucking magnet in the spindle and/or hub assembly provides sufficient force to keep the hub assembly engaged on the spindle motor during rotation. Magnetic chucking provides sufficient engagement in most disk drives that operate at lower rotation speeds, as well as in most disk drive units that are internally mounted in a computer casing.
Applicant has discovered, however, that magnetic chucking is susceptible to failure in higher-speed, stand-alone disk drive units. In particular, Applicant has found that if a stand-alone, removable cartridge disk drive is somehow gyrated while the spindle motor is operating at full speed, such as might occur if a user lifts the disk drive unit off a table or desk and moves it to a different position, the gyroscopic forces that result from such movement can cause the hub assembly of a disk cartridge to separate from the spinning motor. Separation of the hub assembly from the spinning motor is likely to cause severe damage to both the storage medium in the disk cartridge and to the internal components of the disk drive.
Accordingly, there is a need for a mechanism that prevents separation of the hub assembly from the spindle motor in such situations. The present invention satisfies this need.